New research directions in the last decade have led to major developments in the uses of plant lectins in bioscience and biomedicine. Major advances have been made in our understanding how lectins in the diet can act on the gastrointestinal tract and the physiological consequences of their actions, and how they can modulate body- and organ metabolism, the immune system and the gut microflora. Particularly striking progress has been made in unravelling the effects, often beneficial, of both orally- and parenterally administered lectins, including lectins of Viscum album-, Phaseolus vulgaris-, Robinia pseudoacacia, Agaricus bisporus, etc on tumours and in cancer therapy. Results have also made it possible to devise and try out other beneficial applications of plant lectins as gut-, metabolic- and hormonal regulators, immune reagents, probiotic/prebiotic oral supplements and to develop methods based on the oral application of lectins to protect the intestines against the often lethally harmful effects of chemo- and radiotherapy. With the development of genetically modified (GM) plants by transferring the genes of some of the natural insecticidal lectins such as the various Bacillus thuringiensis lectin-Cry toxins or some insecticidal plant lectins to major crop plants, a possible new avenue in plant protection may have opened up.